In urban areas, gonorrhea incidence has a consistent geographic distribution characterized by high disease incidence rates in defined "core" areas, and decreased incidence as the radial distance : from the central core increases. "Core" area geographic subunits are usually defined as the group of census tracts which account for 50% of disease morbidity in a defined community. The core theory of STD transmission postulates that eradicating disease in the "core", will result in overall community-wide decreases in gonorrhea rates. We have developed a computerized clinical record and morbidity reporting system which provides the data management infrastructure necessary to evaluate the core theory. By using Geographic Information System (GlS) mapping and developing census-tract specific rates, we have identified two hyperendemic "cores" of gonorrhea incidence, one in East and West Baltimore. These two communities are demographically equivalent but have very little crossover utilization of public health or medical services. Initially, we propose to further refine our GlS-linked disease reporting system, to include both public-clinic and private sector gonorrhea morbidity. We then will perform a controlled intervention trial for gonorrhea with East Baltimore as the enhanced intervention condition. In West Baltimore we will continue the current practice of partner self- referral. The intervention will be focused-it will be applied only to patients with gonorrhea who reside in the "core area" census tracts, and will consist of an interview to identify sexual partners and members of the infected individuals's social network. We will perform aggressive field outreach to contact identified individuals and use non-invasive urine-based DNA-amplification tests for gonorrhea and other STDs. Sexual partners will be treated presumptively; others will be treated based on test results. We hypothesize that aggressive, focused intervention will result in decreased "core" area gonorrhea rates. The non-intervention clinic will provide a control group to account for overall secular trends in gonorrhea. Social network and sex partner data will help in focusing control measures for developing models of disease transmission. If the "core theory" is correct subsequent decreases of disease incidence will occur in census tracts adjacent to the "core", and will provide a model to implement STD control interventions in high-incidence urban areas.